The present invention relates generally to transmission of fiber-optic signals and, more particularly, to a collimator for transforming the output from one or more optical fibers into one or more parallel optical beams.
Many fiber-optic devices r that the output from one or more optical fibers be converted into collimated beams. A fiber optic collimator takes light from a optical fiber and generates a beam of collimated light at an increased specified diameter. The collimator desirably maintains alignment between the fiber and the collimating lens When two or more optical fibers are coupled to the same collimator (referred to as expanded beam coupling), high precision alignment of the respective fibers is necessary. Previous fiber optic collimators tend to be clumsy, employ complex mechanisms, and are difficult to assemble and adjust for focus and alignment.
Embodiments of the present invention are directed to a compact and stable fiber optic collimator that takes light from one or more optical fibers and generates one or more beams of collimated light at an increased specified diameter. The optical fibers are connected to a single collimator body having precise collimator bores for receiving and aligning the optical fibers relative to the respective collimating lenses. Each lens is configured to be adjustable along its plane for aliment with respect to the tip of the corresponding optical fiber. The optical fiber is configured to be adjustable along an axis of the collimator bore to focus the light beam to obtain the desired wavefront quality. After a first set of optical fiber and collimating lens are aligned, the other sets of optical fiber and collimating lens may be aligned with respect to the first set The collimator is designed to achieve a substantially athermal configuration. The collimator is stable over a specific soak temperature range and maintains alignment through adverse vibration. The collimator is configured for easy assembly and for simple and precise adjustment.
In accordance with an aspect of the present invention, a fiber optic collimator comprises a shuttle plug including a cavity for receiving an optical fiber having an optical fiber tip to emit a light through the shuttle plug. A collimator body has a collimator bore to receive the shuttle plug and constrain the shuttle plug in the collimator bore to be movable in an axial direction along an axis of the collimator bore. A collimating lens is mounted to the collimator body and disposed generally opposite from the optical fiber tip to receive a light beam from the optical fiber tip expanding in size toward the collimating lens. The collimating lens is constrained to be movable in a transverse plane normal to the axial direction. The shuttle plug is configured to be movable in the axial direction to adjust a position of the optical fiber tip with respect to the collimating lens and the collimating lens is configured to be movable in the transverse plane to align the collimating lens with respect to the optical fiber tip.
In some embodiments, the shuttle plug includes a fiber optic ferrule to attach the optical fiber and position the optical fiber tip within the shuttle plug. The shuttle plug includes a pin keyway and the collimator body includes a rotation alignment pin configured to engage the pin keyway to prevent rotation of the shuttle plug with respect to the collimator body. The fiber optic ferrule is rotationally aligned with respect to the pin keyway for desired polarization of the light beam from the optical fiber. The fiber optic ferrule is connected to the shuttle plug by an adhesive introduced into adhesive tack bond holes in the shuttle plug at two axial locations along the fiber optic ferrule (e.g., six adhesive tack bond holes at two axial locations, 120 degrees apart). The shuttle plug includes an undercut diameter intermediate region between two end regions, and wherein the two end regions each include machined flats to reduce surface contact with the bore of the collimator body (e.g., three 120 degrees opposed machined flats). The shuttle plug is connected to the collimator body by an adhesive introduced into adhesive tack bond holes in the collimator body at two axial locations along the shuttle plug (e.g., six adhesive tack bond
holes at two axial locations, 120 degrees apart).
In specific embodiments, a lens cell has a seat to receive the collimating lens. The lens cell is configured to mount the collimating lens to the collimator body to permit adjustment in the transverse plane normal to the axial direction to align the collimating lens with respect to the optical fiber tip. The lens cell is connected to the collimator body by an adhesive introduced into adhesive tack bond holes in the collimator body distributed around the lens cell. The lens cell is attached to the collimator body by a plurality of cell clamps (which is desirable in severe environments). The collimator body includes a plurality of raised pads (e.g., three pads) which are coplanar and parallel to the axis of the collimator bore. The raised pads are configured to interface with a mating piece to which the collimator body is to be connected. The collimator body may include a plurality of collimator bores to receive a plurality of shuttle plugs, and the collimator body is configured to mount a plurality of collimating lenses each for alignment and focus with respect to a corresponding one of the plurality of shuttle plugs.
In accordance with another aspect of the invention, a fiber optic collimator comprises a shuttle plug including a cavity for receiving an optical fiber having an optical fiber tip to emit a light through the shuttle plug. A collimator body has a collimator bore to receive the shuttle plug and constrain the shuttle plug in the collimator bore to be movable in an axial direction along an axis of the collimator bore. A lens cell has a seat to receive a collimating lens, and is configured to mount the collimating lens to the collimator body generally opposite from the optical fiber tip to receive a light beam from the optical fiber tip expanding in size toward the collimating lens and to permit adjustment of the collimating lens in a transverse plane normal to the axial direction to align the collimating lens with respect to the optical fiber tip.
In some embodiments, the lens cell is connected to the collimator body by an adhesive introduced into adhesive tack bond holes in the collimator body distributed around the lens cell. The lens cell is attached to the collimator body by a plurality of cell clamps.
In accordance with another aspect of the invention, a method of mounting an optical fiber and a collimating lens to a collimator body comprises mounting an optical fiber to a shuttle plug, the optical fiber having an optical fiber tip to emit a light through the shuttle plug; and sliding the shuttle plug into a collimator bore of the collimator body configured to receive the shuttle plug and constrain the shuttle plug in the collimator bore to be movable in an axial direction along an axis of the collimator bore. A collimating lens is mounted to the collimator body to be disposed generally opposite from the optical fiber tip to receive a light beam from the optical fiber tip expanding in size toward the collimating lens. The shuttle plug is moved in the axial direction to adjust a position of the optical fiber tip with respect to the collimating lens.
In some embodiments, mounting the collimating lens comprises placing the collimating lens in a seat of a lens cell; coupling the lens cell to the collimator body to permit adjustment in a transverse plane normal to the axial direction; moving the lens cell with respect to the collimator body in the transverse plane to align the collimating lens with respect to the optical fiber tip; and attaching the lens cell to the collimator body after the collimating lens is aligned with respect to the optical fiber tip. Moving the lens cell comprises connecting the lens cell to two linear stages configured to move the lens cell in two orthogonal directions along the transverse plane. Moving the shuttle plug comprises coupling a focus tooling member with the shuttle plug by supporting a focus tooling rod using a focus tooling clamp temporarily coupled to the collimator body. The focus tooling member is connected to a linear stage configured to move the shuttle plug in the axial direction to focus the optical fiber tip with respect to the collimating lens. The method further comprises attaching the shuttle plug to the collimator body and removing the focus tooling rod and the focus tooling clamp after focusing the optical fiber tip with respect to the collimating lens.
In specific embodiments, mounting the optical fiber comprises coupling the optical fiber to a fiber optic ferrule and attaching the fiber optic ferrule to the shuttle plug to position the optical fiber tip within the shuttle plug. The shuttle plug includes a pin keyway, and the fiber optic ferrule is rotationally aligned with respect to the pin keyway for desired polarization of the light beam from the optical fiber. A rotation alignment pin is inserted through a portion of the collimator body to engage the pin keyway to prevent rotation of the shuttle plug with respect to the collimator body. The collimator body includes a plurality of raised pads (e.g., three raised pads) which are coplanar and parallel to the axis of the collimator bore. The method further comprises interfacing the raised pads with a mating piece to which the collimator body is to be connected. The method further comprises providing a pin extending from two raised pads of the collimator body to two oversized pin holes in the mating piece; wet-pinning the pin to the mating piece by introducing an adhesive into the oversized pin holes; and attaching the collimator body to the mating piece by a plurality of screws. This process mitigates against drilling.